The Bombardier Beetle Myth Exploded

Dr. Duane T. Gish, assistant director of the Institute for Creation Research (ICR)
has made some extravagant and unfounded claims about the bombardier beetle
(genus Brachinus). This beetle defends itself by shooting boiling-hot fluids out
its rear end at its attackers; Gish argues that no ordinary beetle could have
slowly evolved into a bombardier beetle through any conceivable transitional
forms because a transitional beetle with an incomplete mechanism would have
either been burdened with a load of useless baggage, or else have blown itself
to smithereens. In this article, we shall see how badly Gish has distorted the
facts about this insect.

In his book Dinosaurs: Those Terrible Lizards (Creation-Life Publishers: San
Diego, CA, 1977), Gish lays out his entire argument that transitional beetles
are inconceivable. He describes how the bombardier beetle's explosive defense
system is supposed to work, claiming to derive his information from the German
entomologist Dr. Hermann Schildknecht. His argument is based on this description
of the beetle's mechanism, and stands or falls with it:

This scientist [Dr. Hermann Schildknecht] found out, first of all, that the
bombardier beetle mixes up two kinds of chemicals—hydrogen peroxide and
hydroquinone. Now the marvelous thing about this is, if you or I went into a
chemistry laboratory and mixed up these two chemicals — BOOM! We would blow
ourselves up.

But not the bombardier beetle. He's too smart. When he mixes up these two
chemicals he makes sure he adds another kind of chemical, called an inhibitor.
The inhibitor somehow prevents the other two chemicals from blowing up. In other
words, they just sit there together real peaceful like. The beetle then stores
this liquid in two storage chambers, ready to be used when needed. . . .

How does Mr. B. B. make the chemical solution explode just at the right time, in
spite of the fact that it contains an inhibitor? Dr. Schildknecht found out just
at the exact moment Mr. B. B. wants to
fire his two cannons, he squirts in an anti-inhibitor. The antiinhibitor
neutralizes (knocks out) the inhibitor, and the two chemicals (the hydrogen
peroxide and the hydroquinone) can then react violently together and explode. (pp. 51-52)

- page 2 -

Thus Gish is maintaining that the bombardier beetle juggles four chemicals in
its defense mechanism. The hydrogen peroxide and hydroquinone spontaneously
explode unless an inhibitor is added to prevent the explosion. The beetle fires
off its defense mechanism by adding an anti-inhibitor to this mixture. Gish
bases his entire argument on this inhibitor model. If any of the four chemicals,
any of the organs, or the nervous system mechanism were missing in any of the
transitional forms, then either the beetle would blow itself up, or else it
would be lugging around a lot of useless baggage. Obviously, natural selection
would not select for either one. At any rate, that's how Gish argues.

Actually, Dr. Gish totally misrepresents Dr. Schildknecht, who says absolutely
nothing about an inhibitor. On the contrary, hydrogen peroxide and hydroquinone
do not spontaneously blow up when mixed together; they just slowly turn brown as
they oxidize. The only time they explode is when the beetle forces them to by
adding two catalysts, a catalase to decompose the hydrogen peroxide, and a
peroxidase to oxidize the hydroquinones and thereby break them down into the
simpler quinones. Apparently Gish's translator does not read German very well.
Drs. William Thwaites and Frank Awbrey of San Diego State University in
California have even shown Gish there is no inhibitor and that the two explosive
chemicals do not explode spontaneously. Yet despite this, Dr. Gish still
continues to use this false argument.

Thwaites and Awbrey teach a two-model Evolution vs. Creation course at San Diego
State. Leading creationists such as Dr. Gish present the creationist viewpoint
during one session, and then Awbrey and Thwaites present the findings of
empirical science during the following meeting. At one such rebuttal session in
the spring of 1978, Thwaites gingerly mixed hydrogen peroxide and hydroquinone
solutions together. The two professors took elaborate precautions to protect the
class in case Dr. Gish's biochemistry turned out to be correct. The solutions
only turned brown, failing to explode.

This is an easy experiment to duplicate. You- can even try it at home, since
hydroquinone can be purchased from your local photography shop (it's used for
photographic developer), and hydrogen peroxide is available at your supermarket
or drug store (it's used in women's hair coloring). This allows you to prove to
your own satisfaction that hydrogen peroxide and hydroquinone do not
spontaneously explode.

When Thwaites and Awbrey confronted Gish with this fact, he became flustered,
and said that somehow the German word for "unstable" had been mistranslated as
"explosive."

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When they asked him what his source was, he
replied that he had gotten his information from Hermann Schildknecht, Eleonore
Maschwitz. and U. Maschwitz. "Die Explosionschemie der Bombardierkafer (Coleoptera,
Carabidae)," Zeitschrift fur Naturforschung, Vol. 23 (1968), pp. 1213-1218. The
purpose of this article is to study the nature of the catalysts that make the
otherwise inert hydrogen peroxide and hydroquinone explode:

During the "pop," the contents of the paired pygidial defense bladders of the
bombardier beetle (hydrogen peroxide and hydroquinone) are squeezed in small
portions into chitinous chambers, and there they are explosively transformed
into oxygen, quinone, and water. This explosion-chamber reaction is catalyzed by
enzymes, which are emptied as a dark brown 40-60% albumin solution out of
one-celled annex-glands into the front chamber. [My own translation]

Thus Schildknecht is saying that the hydrogen peroxide and hydroquinone do not
explode until the enzymes make them do so, and mentions nothing about any
inhibitor. Let us see in more detail what Schildknecht has to say on the
beetle's explosion mechanism.

Schildknecht's diagram of the insect's defense organs shows that there are two
chambers, the larger inner chamber (called the "reservoir" by Eisner and the
"collection bladder" by Schildknecht) empties into the smaller outer one (called
the "vestibule" by Eisner and the "explosion chamber" by Schildknecht), which in
turn empties into the outside world through an opening near the anus. There are two sets of these organs, one on either side of the anus. The collection bladder collects hydrogen peroxide and hydroquinone, which just sit there without exploding. The explosion chamber collects a brown gooey mixture of enzymes. This chamber has a thick chitin wall with numerous little holes in it through which single-celled glands secrete and deposit the enzymes into the chamber. When the insect becomes excited, a muscle opens up a little door on a hinge. Through this opening the two chemicals are forced into the explosion chamber, where the enzymes make them explode out of the insect's derriere as oxygen, quinone, and water. (The door opens into the explosion chamber so that the explosion will force the door shut and not injure the collection bladder. Schildknecht explains the chemistry of this reaction clearly:

Not only did the results of our earlier work on the defense system of the bombardier beetle give the surprising result that this beetle manufactures a 25% solution of hydrogen peroxide and a 10% solution of hydroquinone, but we can now also show that the enzyme that sparks off these chemicals is also stored in an extraordinarily high concentration. In the explosion chamber a 40-60% albumin solution is stored which consists of one third peroxidase and two thirds catalase. We are concerned here with the secretion of the annex-glands which empty into the front chamber of the pygidial bladder, an extension of the anus.

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Gish was made aware of all this in the spring of 1978. Even though he continued
to insist that this insect could not have evolved and that it has some kind of
inhibitor to keep the two chemicals from oxidizing, he reluctantly admitted that
hydrogen peroxide and hydroquinone do not spontaneously explode when
mixed, and that Schildknecht has nothing to say about any inhibitor.

Nevertheless, Gish still continues to use his old description in his debates.
For instance, on January 17, 1980, in a debate with Dr. John W. Patterson at
Graceland College, Lamoni, Iowa, Gish said:

The bombardier beetle is a remarkable little creature that has this explosive
mechanism. He stores two chemicals in a storage chamber, and he puts in an
inhibitor to keep it from exploding or decomposing. He squirts it in the
combustion tube, and then he adds an antiinhibitor, and there all the enzymes
there [sic]—and boom! An explosion goes off right in the face of his enemy.
Beautifully timed! Beautiful mechanism! You have to have thick storage chambers,
you have to have the two chemicals, you have to have an inhibitor, you have to
have an anti-inhibitor, you've got to have those combustion tubes, you have to
have the communication network all present and functioning, just as you have to
have every part on the rockets to go to the moon present and functioning. How
are you going to explain that step-by-step by evolution by natural selection? It
cannot be done!

Gish already knew better. Why would he repeat an old error? If he is this
unreliable in areas where we can check up on him, then how can we trust him in
areas where we cannot? But even if his facts were beyond reproach, we would
still have difficulty taking him seriously because he brings up the bombardier
beetle to help prove that fire-breathing dragons may have actually existed. In
the very book in which he describes the bombardier beetle (Dinosaurs: Those
Terrible Lizards), he argues that old legends, Job 41:18-21, and the bombardier
beetle all suggest that the unique crests on the heads of some duck-billed
dinosaurs were the chemical storage tanks for their flame-throwing mechanisms.
These dinosaurs were thus the fire-breathing dragons of myth and legend! Need I
say more?

Although the main purpose of this article is to show that Gish's description
cannot be trusted, we should take a little time to see how the bombardier
beetle's defense mechanism could have gradually evolved. There's no problem
explaining where the hydroquinone and the hydrogen peroxide came from.

- page 5 -

As Thomas Eisner shows in his article "Chemical Defense Against Predation in
Arthropods" (Chemical Ecology, 1970, pp. 157-215), hydrogen peroxide is a normal
metabolic byproduct in insects, and various quinones are used to harden (or "sclerotinize")
the cuticle of insects. All kinds of insects therefore secrete these chemicals.
As a byproduct, hydroquinone tastes bad to predators and is the chemical that
makes stink bugs stink. So, if an insect's cuticle became indented, forming
little sacs to store some of this hydroquinone, it would have an advantage over
its fellows even if its storage mechanism was not yet very efficient.

Schildknecht himself points out that the carabid family of beetles has little
sacs like this. They have glands that exude enzymes into pygidial bladders that
empty into the anus, even though these don't explode. So, even though the
bombardier beetle is the only carabid beetle to shoot boiling liquid at its
enemies, the other carabid beetles, living in different ecological niches,
survive very well because, with their thick-walled little sacs, they can poison
their enemies but not themselves.

Therefore, all the pre-bombardier beetle had to do was direct some of that
hydrogen peroxide into its collection bladder, develop a little valve between
the collection bladder and vestibule chamber, and finally supply the catalase
and peroxidase in the vestibule. The hydrogen peroxide would make the insect
more poisonous to eat than it was before. A muscle that pulled the duct between
the two chambers open, and relaxed to let it close, would help the beetle be
more selective about its poison discharges. Even if this valve structure was
crude at first, it would have survival value until the side of the duct attached
to the muscle could evolve into a little door. The enzymes would be useful the
moment they appeared. Even if the beetle's new firing mechanism could not be
aimed all that well or if the chemicals were not being secreted in the best
proportions at first, the mechanism would still be useful from the start, and
the beetle could refine it in time.

So, when Gish says, "How are you going to explain that step-by-step by evolution
by natural selection? It cannot be done!" he is merely admitting that he has
little ability in problem solving.

About the Author(s):

Chris Weber, one of the editors of this journal, is a computer programmer who
has followed the creation/evolution controversy for over seven years. All the
German translations in this article are his own.